U.S. patent number 8,291,743 [Application Number 12/473,159] was granted by the patent office on 2012-10-23 for method and system for calibrating an electronic lapping guide for a beveled pole in a magnetic recording transducer.
This patent grant is currently assigned to Western Digital (Fremont), LLC. Invention is credited to Ming Jiang, Changqing Shi.
United States Patent |
8,291,743 |
Shi , et al. |
October 23, 2012 |
Method and system for calibrating an electronic lapping guide for a
beveled pole in a magnetic recording transducer
Abstract
A method and system for calibrating an electronic lapping guide
(ELG) for transducer(s) having an ABS and a magnetic structure are
described. The magnetic structure has a desired thickness, a bevel,
and a flare point a distance from the ABS. The method and system
include providing at least three ELGs. A first ELG has first and
second edges first and second distances from the ABS. A second ELG
has third and fourth edges third and second distances from the ABS.
A third ELG has fifth and sixth edges fourth and second distances
from the ABS. The first, third, and fourth distances correspond to
a stripe height and an offset. The first, third, and fourth
distance and/or the second distance corresponds to an intersection
between the bevel and the desired thickness. The method and system
also include measuring resistances of the ELGs, and calibrating the
ELG(s) utilizing the offset and resistances.
Inventors: |
Shi; Changqing (San Ramon,
CA), Jiang; Ming (San Jose, CA) |
Assignee: |
Western Digital (Fremont), LLC
(Fremont, CA)
|
Family
ID: |
47017283 |
Appl.
No.: |
12/473,159 |
Filed: |
May 27, 2009 |
Current U.S.
Class: |
73/1.01;
702/104 |
Current CPC
Class: |
G11B
5/3169 (20130101); G11B 5/3166 (20130101) |
Current International
Class: |
G01N
37/00 (20060101); G11B 27/36 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Matsushita, et al., "Elaborate Precision Machining Technologies for
Creating High Added Value at Low Cost", Fujitsu Sci. Tech. J., 43,
1, pp. 67-75, Jan. 2007. cited by other.
|
Primary Examiner: Larkin; Daniel
Claims
We claim:
1. A method for calibrating an electronic lapping guide (ELG) for
least one transducer having an air-bearing surface (ABS) and a
magnetic structure, the magnetic structure having a desired
thickness, a bevel, and a flare point a distance from the ABS, the
method further comprising: providing at least a first ELG, a second
ELG, and a third ELG, the first ELG having a first edge a first
distance from the ABS and a second edge a second distance from the
ABS, at least one of the first distance and the second distance
corresponding to an intersection between the bevel and the desired
thickness, the second ELG having a third edge a third distance from
the ABS and a fourth edge the second distance from the ABS, at
least one of the third distance and the second distance
corresponding to the intersection between the bevel and the desired
thickness, the third ELG having a fifth edge a fourth distance from
the ABS and a sixth edge the second distance from the ABS, the
first distance, the third distance, and the fourth distance
corresponding to a stripe height and an offset, at least one of the
fourth distance and the second distance corresponding to the
intersection between the bevel and the desired thickness; measuring
resistances of the first ELG, the second ELG, and the third ELG;
and calibrating the at least one of the first ELG, the second ELG,
and the third ELG utilizing the offset and the resistances.
2. The method of claim 1 wherein the magnetic structure is a pole
having the bevel and a plurality of sides, the plurality of sides
having a reverse angle.
3. The method of claim 1 further wherein the step of calibrating
further includes: determining the stripe height, a target
resistance, and a sheet resistance of the at least one of the first
ELG, the second ELG and the third ELG.
4. The method of claim 3 wherein the step of providing the at least
the first ELG, the second ELG, and a third ELG utilizes a reticle
to provide a mask and wherein the step of providing the at least
the first ELG, the second ELG, and a third ELG further includes:
shifting the reticle between the first ELG, the second ELG, and the
third ELG to provide the offset between the first ELG, the second
ELG, and the third ELG in the mask.
5. The method of claim 1 wherein the second distance corresponds to
an intersection between the bevel and the desired thickness.
6. The method of claim 1 wherein the first distance, the third
distance, and the fourth distance each corresponds to an
intersection between the bevel and the desired thickness.
7. The method of claim 1 wherein the first distance is the third
distance minus the offset and the fourth distance is the third
distance plus the offset.
8. The method of claim 1 wherein the step of providing the at least
the first ELG, the second ELG and the third ELG further includes:
providing a fourth ELG having a seventh edge a fifth distance from
the ABS and an eighth edge a second distance from the ABS, at least
one of the seventh distance and the second distance corresponding
to an intersection between the bevel and the desired thickness.
9. The method of claim 8 wherein the step of measuring the
resistances further includes: measuring resistance of the fourth
ELG.
10. The method of claim 9 wherein the step of calibrating the at
least one ELG further includes calibrating the at least one ELG
utilizing the resistance.
11. A method for calibrating an electronic lapping guide (ELG) for
least one transducer having an air-bearing surface (ABS) and a
pole, the pole having a desired thickness, a bevel, and a flare
point a distance from the ABS, the method further comprising:
providing a resistive sheet substantially coplanar with the desired
thickness; providing at least a first ELG, a second ELG, and a
third ELG from the resistive sheet, the first ELG having a first
edge a first distance from the ABS and a second edge a second
distance from the ABS, at least one of the first distance and the
second distance corresponding to an intersection between the bevel
and the desired thickness, the second ELG having a third edge a
third distance from the ABS and a fourth edge the second distance
from the ABS, at least one of the third distance and the second
distance corresponding to the intersection between the bevel and
the desired thickness, the third ELG having a fifth edge a fourth
distance from the ABS and a sixth edge the second distance from the
ABS, the first distance, the third distance, and the fourth
distance corresponding to a stripe height and an offset, at least
one of the fifth distance and the second distance corresponding to
the intersection between the bevel and the desired thickness, the
first distance being the third distance plus the offset, the fourth
distance being the third distance minus the offset, the step of
providing the at least the first ELG, the second ELG, and a third
ELG utilizing a reticle to provide a mask, the reticle being
shifted between the first ELG, the second ELG, and the third ELG to
provide the offset between the first ELG, the second ELG, and the
third ELG in the mask; measuring resistances of the first ELG, the
second ELG, and the third ELG; and calibrating the at least one of
the ELG, the second ELG and the third ELG utilizing the offset and
the resistances.
Description
BACKGROUND
Conventional magnetic heads typically employ lapping to fabricate
structures within the head. For example, lapping is typically used
in processing a write transducer. More specifically, after pole
formation, lapping may be used to remove a portion of the device to
expose the air-bearing surface (ABS). Lapping determines the
windage, the length measured from the ABS to the flare point of the
pole of the write transducer. The windage, or nose length, is the
distance from the ABS at which the angle the sides of the pole make
with a plane parallel to the ABS increases. Similarly, lapping may
be used in fabricating other structures in a head, such as the read
sensor of a conventional read transducer.
In order to control lapping an electronic lapping guide (ELG) is
typically used. FIG. 1 depicts a top view of a conventional ELG 10.
The conventional ELG 10 is essentially a resistive stripe. Thus,
the conventional ELG 10 is coupled with leads 14 and 16 that are
used to determine the resistance of the conventional ELG 10. The
conventional ELG has a length l from the surface 12 being lapped.
As lapping continues, the surface 12 is worn away, and the length
of the conventional ELG 10 decreases. As the length is reduced, the
resistance of the conventional ELG 10 increases. Using the
resistance of the conventional ELG 10, it can be determined when
lapping should be terminated.
FIG. 2 is a flow chart depicting a conventional method 30 for
performing lapping using the conventional ELG. The conventional
method 30 is described in the context of the conventional ELG 10.
The resistance of the conventional ELG 10 is measured during
lapping of the transducer, via step 32. The current length of the
conventional ELG 10 is determined based upon the resistance
measured in step 32 and the sheet resistance of the conventional
ELG 10, via step 34. The sheet resistance may be determined in a
conventional manner using a conventional Van der Pauw pattern (not
shown) provided on the substrate on which the magnetic transducer
is to be fabricated. The conventional Van der Pauw test pattern is
a well known pattern that may be used to determine sheet resistance
of a stripe, such as the conventional ELG 10. Thus, after step 34,
the length corresponding to a particular measured resistance for
the conventional ELG 10 is known. Alternatively, step 34 could
simply convert a desired windage to an ELG length and the ELG
length to a desired target resistance of the conventional ELG
10.
The lapping is terminated when the resistance of the conventional
ELG 10 indicates that the desired length or target resistance of
the conventional ELG 10 has been reached, via step 36. Because the
conventional ELG 10 and structure, such as a read sensor or pole,
both exist on the transducer being lapped, the lengths of the
conventional ELG 10 and the structure change with lapping.
Consequently, the lengths of the read sensor or pole may also be
set in step 36.
Although the conventional method 30 and conventional ELG 10
function, the desired windage or other desired length may not be
easily determined for certain structures. For example, FIG. 3
depicts ABS, side, and top views of a conventional perpendicular
magnetic recording (PMR) pole 40 that has a trailing edge bevel 42.
For simplicity, FIG. 3 is not to scale. The conventional PMR pole
40 also has sidewalls 44 having a reverse angle and flare point 46.
Stated differently, the conventional PMR pole 40 has a top wider
than its bottom. Because of the combination of the bevel 42 and
sidewalls 44, the windage, the track width, and the pole height
change as part of the PMR pole 40 is lapped away. Thus, the
geometry of the conventional PMR pole 40 make lapping to the
desired windage (nl), track width (tw), and pole height (H)
challenging. In addition, there are processing variations that
occur for the separate processes used in determining the flare
point 46, bevel 42, and sidewalls 44. Variations in these processes
may cause variations in the shape or location of these features of
the conventional PMR pole 40. It would be desirable, therefore, to
compensate for these processing variations. Use of the conventional
ELG 10 is not sufficient to do so.
Accordingly, what is needed is an improved method for providing and
using an ELG in a magnetic transducer.
SUMMARY
A method and system for calibrating an electronic lapping guide
(ELG) for least one transducer having an air-bearing surface (ABS)
and a magnetic structure is described. The magnetic structure has a
desired thickness, a bevel, and a flare point a distance from the
ABS. The method and system include providing at least three ELGs.
The first ELG has first and second edges first and second distances
from the ABS. The first distance and/or the second distance
correspond to an intersection between the bevel and the desired
thickness. The second ELG has a third edge a third distance from
the ABS and a fourth edge the second distance from the ABS. The
third distance and/or the second distance correspond to the
intersection between the bevel and the desired thickness. The third
ELG has a fifth edge a fourth distance from the ABS and a sixth
edge the second distance from the ABS. The first distance, the
third distance, and the fourth distance correspond to a stripe
height and an offset. The fourth distance and/or the second
distance correspond to the intersection between the bevel and the
desired thickness. The method and system also include measuring
resistances of the first ELG, the second ELG, and the third ELG and
calibrating the at least one ELG utilizing the offset and the
resistances.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 depicts a conventional ELG as used in a conventional
magnetic transducer.
FIG. 2 is a flow chart depicting a conventional method for
performing lapping utilizing a conventional ELG.
FIG. 3 depicts a conventional PMR pole in a conventional PMR
transducer.
FIG. 4 is a flow chart depicting an exemplary embodiment of a
method for calibrating ELGs.
FIG. 5 depicts an exemplary embodiment of a transducer including a
magnetic structure to be lapped using the ELGs.
FIG. 6 depicts another exemplary embodiment of a transducer
including the ELGs.
FIG. 7 depicts another exemplary embodiment of a transducer
including the ELGs.
FIG. 8 depicts another exemplary embodiment of a transducer
including the ELGs.
FIG. 9 is a flow chart depicting an exemplary embodiment of a
method for calibrating ELGs.
FIGS. 10-11 depict another exemplary embodiment of a transducer
including the ELGs during fabrication of the ELGs.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 4 is a flow chart depicting an exemplary embodiment of a
method 100 for calibrating ELGs. For simplicity, some steps of the
method 100 may be omitted. FIGS. 5-8 depict exemplary embodiments
of a portion of transducers 200, 200', and 200'' with which the
method 100 may be used. For clarity FIGS. 5-8 are not to scale. The
transducers 200, 200', and 200'' each includes at least one
magnetic structure 210 on which lapping is to be performed. The
magnetic structure being fabricated is shown in FIG. 5. Thus, the
transducer in FIG. 5 is labeled 200/200'/200''. In the embodiment
shown, the magnetic structure 210 is a PMR pole having a desired
thickness, h, a bevel 212, and a flare point 216 a distance (NL)
from the ABS. The PMR pole 210 also includes sidewalls 214 having a
reverse angle and is characterized by track width TW. The
transducers 200, 200', and 200'' may be part of a merged head
including a read transducer and the write transducer. The
transducers 200, 200', and 200'' may thus be fabricated on wafer(s)
which hold numerous transducers (not shown). Once fabrication is
complete, or at some other point in processing, the transducers
200, 200', and 200'' may be separated from the wafer(s) on which
they were fabricated and incorporated into a hard disk drive. The
transducers 200, 200', and 200'' may each reside on a slider (not
shown). Although depicted in FIG. 5 as PMR pole 210, a magnetic
structure may include any structure formed in a magnetic
transducer. In various embodiments, other numbers of ELGs per
transducer and/or per magnetic structure, including greater or less
than three per transducer/magnetic structure, may be used. Further,
the method 100 and transducers 200, 200', and 200'' are described
in the context of a flare point 216 and bevel 212. The flare point
corresponds to a point of interest from which distance to the
desired ABS/surface, such as a windage, is measured. Consequently,
in some embodiments, the magnetic structure fabricated using the
method 100 may include some other feature corresponding to the
flare point. Similarly, the bevel corresponds to a surface, top or
bottom, of the magnetic structure 210 which is not perpendicular to
the ABS or which otherwise defines a location of interest on the
magnetic structure. The method 100 is also described in the context
of single transducers 200, 200', and 200''. However, the method 100
may be used for fabricating multiple transducers and/or multiple
structures and may employ multiple ELG(s) at substantially the same
time. The magnetic structure 210 being fabricated has may be
desired to adjoin the ABS. Thus, in the embodiment shown, the
lapping to be performed based on calibration using the method 100
proceeds to the ABS location (the location at which the ABS is
formed). However, in another embodiment, the lapping may be used to
expose another surface.
At least three ELGs having the desired offsets and stripe heights
are provided, via step 102. Thus, at least a first ELG, a second
ELG, and a third ELG are formed. Step 102 may include depositing a
resistive sheet and fabricating the three or more ELGs from the
resistive sheet. The ELGs are configured so that one of their edges
correspond to a particular position, such as the intersection
between the bevel 212 and the desired thickness h. Such a position
may correspond to the desired location of the ABS. However, another
location such as the flare point may also be selected. The ELGs are
also configured in step 102 such that another edge corresponds to
the desired stripe height and an offset. For three ELGs, the other
edges may correspond to the stripe height, the stripe height plus
an offset, and the stripe height minus an offset. Stated
differently, the locations of the other edges of the three or more
ELGs may be expressed in terms of two variables (e.g. the stripe
height and an offset). The ELGs may be fabricated by using a single
mask and shifting the reticle a known amount between the different
ELGs. Shirting the reticle may provide the most reliable
determination of the offsets. Portions of the ELGs may be removed
to the same location, such as the intersection of bevel and the
desired height. However, in another embodiment, another method for
providing the offsets may be used.
FIG. 6 depicts one embodiment of a transducer 200 after step 102 is
performed. Thus, three ELGs 220, 230, and 240 are shown. The ELGs
220, 230, and 240 have edges 222, 232, and 242, respectively, at a
location defined by the intersection of the bevel and the desired
height. The other edges 224, 234, and 244 are located at the stripe
height plus an offset (SH+.delta.), the stripe height (SH) and the
stripe height minus an offset (SH-.delta.) from the bevel location.
Thus, each of the ELGs 220, 230, and 240 has a common location and
lengths that differ in known ways.
FIG. 7 depicts another embodiment of a transducer 200' after step
102 is performed. Thus, three ELGs 220', 230', and 240' are shown.
The ELGs 220', 230', and 240' have edges 224', 234', and 244',
respectively, at a known location. In the embodiment shown, the
edges 224', 234', and 244' may be at the flare point. The other
edges 224', 234', and 244' are located at the stripe height plus an
offset (SH+.delta.), the stripe height (SH) and the stripe height
minus an offset (SH-.delta.) from the flare point. Thus, each of
the ELGs 220', 230', and 240' has a common location and lengths
that differ in known ways.
FIG. 8 depicts another embodiment of a transducer 200'' after step
102 is performed. In this embodiment, four ELGs 220'', 230'',
240'', and 250 are shown. The ELGs 220'', 230'', 240'', and 250
have edges 222'', 232'', 242'', and 252 respectively, at a known
location. In the embodiment shown, the edges 222'', 232'', 242'',
and 252 may be at the intersection between the bevel 212 and the
desired height h (i.e. at the desired ABS). The other edges 224'',
234'', 244'', and 254 are located at the stripe height plus an
offset (SH+.delta.), the stripe height (SH) the stripe height minus
an offset (SH-.delta.), and the stripe height plus twice the offset
(SH+2.delta.) from the bevel 212-height intersection. The offset,
d, may vary. In some embodiments, .delta. may be at least fifty
nanometers and not more than one hundred nanometers. However, the
offset .delta. may vary based on the structure 210 being fabricated
and is generally desired to be in the process window range. Thus,
each of the ELGs 220'', 230'', 240'', and 250 has a common location
and lengths that differ in known ways.
The resistances of the ELGs are measured, via step 104. Thus, for
the transducer 200, the resistances of the ELGs 220, 230, and 240
are determined. For the transducer 200', the resistances of the
ELGs 220', 230', and 240' are determined. For the transducer 200'',
the resistances of the ELGs 220'', 230'', 240'', and 250 are
determined.
The ELGs are calibrated using the offset and the resistances, via
step 106. Step 106 may include determining the stripe height, a
target resistance of each ELG, and a sheet resistance of the ELGs.
The calibration may be determined using a linear model for the
resistances. For example, for the transducer 200, the resistances
of the ELGs 220, 230, and 240 are given by:
R.sub.220=R.sub.L+R.sub.S*{W/(SH+.delta.)};
R.sub.230=R.sub.L+R.sub.S*{W/(SH)}; and
R.sub.240=R.sub.L+R.sub.S*{W/(SH-.delta.)}. These equations may be
solved for the desired stripe height (SH), R.sub.S*W, and R.sub.L.
In particular,
SH=.delta.*(R.sub.240-R.sub.220)/(R.sub.240+R.sub.220-2*R.sub.230),
R.sub.S*W=2*.delta.*(R.sub.240-R.sub.220)*(R.sub.240-R.sub.230)*(R.sub.23-
0-R.sub.220)/[R.sub.220+R.sub.240-2*R.sub.230].sup.2; and
R.sub.L=[2*R.sub.220*R.sub.240-R.sub.240*R.sub.230-R.sub.230*R.sub.220]/(-
R.sub.240+R.sub.220-2*R.sub.230). Consequently, the stripe height
and thus the windage can be determined. If more than three ELGs are
used, then higher order terms or other variables might be taken
into account. Thus, the stripe height and the resistance
coefficient, or resistance per unit length, may be determined.
Using the method 100, the ELGs 220, 230, and 240; the ELGs 220',
230', and 240', and the ELGs 220'', 230'', 240'', and 250 may be
calibrated. For example, the resistance per unit length of the ELGs
may be determined based on the resistances, stripe height, and
offset. In one embodiment, the stripe heights, SH, correspond to
the desired windage because the back edge 234 of the non-offset ELG
230 is desired to be aligned with the flare point 216 of the PMR
pole 210. In addition to the stripe height, the actual windage may
be calculated using the resistance per unit length and measured
resistance of the ELGs during lapping. Because the actual windage
may be determined, variations in processing and other
inconsistencies may be taken into account. In particular, the
actual windage values may be used in lapping the PMR pole 210 or
other analogous structure. Consequently, better control of lapping
and thus better control over the final structure may be achieved.
Improvements in manufacturing and performance of the transducers
200/200'/200'' may thus be accomplished.
FIG. 9 is a flow chart depicting another exemplary embodiment of a
method 150 for calibrating ELGs. For simplicity, some steps of the
method 150 may be omitted. FIGS. 10-11 depict another exemplary
embodiment of a transducer 300 including the ELGs 320, 330, and 340
during fabrication of the ELGs. For clarity, FIGS. 10-11 are not to
scale. The transducer 300 includes a magnetic structure such as the
PMR pole 210 depicted in FIG. 5 and for fabrication of which the
ELGs are desired to be calibrated. In the embodiment shown, the
magnetic structure 210 is a PMR pole having a desired thickness, h,
a bevel 212, and a flare point 216 a distance (NL) from the ABS.
The PMR pole 210 also includes sidewalls 214 having a reverse angle
and is characterized by a track width TW. Note that FIG. 5 depicts
the PMR pole 210 after lapping to the ABS. The transducer 300 is
analogous to the transducer 200. The transducer 300 may thus be
fabricated on wafer(s) which hold numerous transducers (not shown).
Once fabrication is complete, or at some other point in processing,
the transducers may be separated from the wafer(s) on which they
were fabricated and incorporated into a hard disk drive. The
transducer 300 may reside on a slider (not shown). Although
depicted in FIG. 5 as a PMR pole 210, a magnetic structure may
include any structure formed in a magnetic transducer. In various
embodiments, other numbers of ELGs per transducer and/or per
magnetic structure, including greater or less than three per
transducer/magnetic structure, may be used. Further, the method 100
and transducers 200, 200', and 200'' are described in the context
of a flare point 216 and bevel 212. The flare point corresponds to
a point of interest from which distance to the desired ABS, such as
a windage, is measured. Consequently, in some embodiments, the
magnetic structure fabricated using the method 150 may include some
other feature corresponding to the flare point. Similarly, the
bevel corresponds to a surface, top or bottom, of the magnetic
structure 210 which is not perpendicular to the ABS or which
otherwise defines a location of interest on the magnetic structure.
The method 150 is also described in the context of single
transducer 300. However, the method 150 may be used for fabricating
multiple transducers and/or multiple structures and may employ
multiple ELG(s) at substantially the same time. The magnetic
structure 210 being fabricated has may be desired to adjoin the
ABS. Thus, in the embodiment shown, the lapping to be performed
based on calibration using the method 150 proceeds to the ABS
location (the location at which the ABS is formed). However, in
another embodiment, the lapping may be used to expose another
surface.
A resistive sheet substantially coplanar with the desired
thickness, h, of the PMR pole is provided, via step 152. The ELG's
are defined from the resistive sheet such that at least one of
their edges are offset by known amounts, via step 154. In one
embodiment, step 154 is performed by shifting the reticle for each
of the ELGs during mask formation, then using the mask formed by
the shifted reticle to remove portions of the resistive sheet. FIG.
10 depicts the transducer 300 after step 154 has been performed.
Thus, ELGs 320, 330, and 340 are shown. However, in another
embodiment, another number of ELGs may be fabricated. Each ELG has
the same depth, d. However, the front edges 322, 332 and 342 as
well as the back edges 324, 334, and 344 are offset due to the
shift in the reticle. For example, the reticle would be at one
location when the mask for the ELG 320 is formed, shifted by an
amount corresponding to .delta. when the mask for the ELG 330 is
formed, and shifted again by an amount corresponding to .delta.
when the mask for the ELG 340 is formed.
One set of the edges is then set along a line, via step 156. In one
embodiment, portions of the ELGs 320, 330, and 340 near the front
edges 322, 332, and 342, respectively, are removed. In another
embodiment, portions of the ELGs 320, 330, and 340 near the back
edges 324, 334, and 344, respectively, are removed. FIG. 11 depicts
the transducer 300 after step 158 is performed. In the embodiment
shown, the front edges 322', 332', and 342' have been set along the
same line. In one embodiment, this is accomplished by exposing the
ELGs 320, 330, and 340 in the same manner as the PMR pole 210
during formation of the bevel 212. Thus, the same processing step,
such as an ion mill, that forms the bevel also forms the front
edges 322', 332', and 342'. Thus, the front edges 322', 332', and
342' are at locations corresponding to the intersection of the
bevel 212 and the desired height, h, of the PMR pole. Further, the
depth of the ELG 320' is now SH+.delta., the depth of the ELG 330'
is SH, and the depth of the ELG 340' is SH-.delta.. In other
embodiments, the offsets between the ELGs 320', 330', and 340' may
differ as long the relationships between the offsets are known.
Thus, using steps 154 and 156, the ELGs 320', 330', and 340' are
formed.
The resistances of the ELGs 320', 330', and 340' are measured, via
step 158. The ELGs 320', 330', and 340' are then calibrated using
the offset, .delta., and the resistances measured, via step 160. In
one embodiment, the linear model described above may be used in
calibrating the ELGs 320', 330', and 340'. Thus, the stripe height,
SH and offset d, may be calculated. Consequently, the windage
(distance between the ABS and flare point 216) of the PMR pole 210
may be determined.
Using the method 150, the ELGs 320', 330', and 340' may be
calibrated. More specifically, quantities such as the stripe height
and resistance per unit length may be calculated. The lengths of
the ELGs 320', 330', and 340' during lapping may be determined
based on the resistances. The final lengths of the ELGs 320', 330',
and 340' after lapping and thus the actual windage of the PMR pole
210 may also be determined. Because the actual windage may be
determined, variations in processing and other inconsistencies may
be taken into account. In particular, the actual windage values may
be used in lapping the PMR pole 210 or other analogous structure.
Consequently, better control of lapping and thus better control
over the final structure may be achieved. Improvements in
manufacturing and performance of the transducers 200/200'/200'' may
thus be accomplished.
* * * * *